DENVER (CBS4) – Rollin Michael Oliver, the 21-year-old Denver man suspected in a Sunday night shooting that left a Denver police officer dead, acknowledged being a gang member when he was booked into the Denver Jail.

On an “offender alert” form obtained by CBS4, Oliver “claims gang” affiliation, according to the form which mandates that Oliver must be accompanied by two officers at all times and be separated from other inmates.

Oliver is being held without bond for investigation of first-degree murder. He made his first court appearance Monday and was surrounded by six deputies.

Denver police arrested Oliver following the City Park shooting death of DPD Officer Celena Hollis, a 32-year-old single mother who had been with the Denver police force since 2005. She was shot in the head and was pronounced dead at Denver Health Medical Center. Police say Oliver was armed when they took him into custody.

At a Monday morning news conference, city officials downplayed gang connections in the case. Asked if the suspect was a known gang member, Police Chief Robert White responded, “It is unknown if he is a gang member.” But in addition to Oliver’s own booking admission, several Denver officers told CBS4 Oliver was known as an active gang member.

Those same officers said the Sunday night incident was the result of two gang factions sparring in City Park. However Chief White downplayed the possible gang connection.

“We don’t know that to be a fact, we have heard those rumors but it’s unsubstantiated at this time,” White said.

Celena Hollis (credit: Denver Police Department)

Multiple DPD contacts said it was a melee between gang members that preceded the shooting.

Anti-gang activist Terrance Roberts said it was known that gang tensions had been boiling over before the Sunday night shooting.

“It was going to be a potential gang fight’, said Roberts.

He said the type of violence that erupted Sunday in City Park is commonplace in northeast Park Hill.

“This is happening consistently every day,” Roberts said.

He points to two shooting incidents Saturday night and Sunday night outside of his office at 33rd and Hudson which he said were likely gang-related. On Sunday night Roberts was in his office when he said he “heard a gun battle, a small caliber shooting off 15 to 20 rounds.” In one of the shootings he said a man was shot in the face.

“Anybody who says there’s not a gang problem; that’s just stupid,” Roberts said.

Mayor Michael Hancock seemed to be aware of the issue.

“We don’t believe we are seeing evidence of another summer of violence,” he said. “But we aren’t going to allow it to grow in that direction.”